Yes I noted on the Potterton boiler installation instructions that there is a circuit (b-zone valves) where an 'hw valve' is on the inlet whereas for cicuit (c - thermostatic valves) the thermostatic is on the outlet.
The tapstat is obviously siezed (pin only moves about 1 mm c.f roughly 5mm...
Problem - No hot water from cylinder except when using electric immersion heater.
Setup - System corresponds to fully pumped with two way split after pump to a) Drayton Tempus 7 controller controlled valve to rads b) Drayton 2 way tapstat valve on the cylinder inlet with sensor mounted on the...